The technique of thin film deposition by ion beam sputtering is well established. In the typical process an ion beam of relatively heavy ions is directed at a target to cause ejection of atomic particles. These particles are collected on a substrate to form a film. In some variations of the technique, two ion beam sources are used; usually a sputtering beam is directed at a target and the second beam is directed at the depositing film. For a general description of these techniques see Weissmantel, et al., Preparation of Hard Coatings By Ion Beam Methods, 63 Thin Film Solids, 315-325 (1979), which is incorporated herein by reference.
An improved technique for dual beam deposition of thin films has recently been devised. In this technique, a sputtering ion beam is directed at a target and the second ion beam is also directed at the target, rather than at the depositing film. For example, the target may be silicon and the second beam may be hydrogen ions. Improved hydrogenated amorphous silicon films may be prepared by this process. See U.S. patent application Ser. No. 647,208 filed Sept. 4, 1984, assigned to the assignee of the present application, the disclosure of which is incorporated herein by reference. This new technique may also be used to deposit hydrogenated semiconductor alloys by employing two ion beam sources for each element of the alloy film. See U.S. patent application Ser. No. 653,168 filed Sept. 28, 1984 assigned to the assignee of the present application, the disclosure of which is incorporated herein by reference.
While the referenced techniques can provide electronic quality semiconductor films, it is also desirable to deposit high density films for use as diffusion masks in integrated circuit manufacture and for use as corrosion and wear resistant coatings on metals. Amorphous films of acceptable density for such applications are usually achieved only by high temperature post-deposition treatments. The temperatures necessary to improve film density can have a detrimental effect on the substrate, particularly if the substrate is an integrated circuit. Accordingly, there is a need for a low temperature technique for depositing dense amorphous films.